1. Field of the Invention
The present invention generally relates to video tape recorders and, more particularly, is directed to a video tape recorder having a built-in type camera in which a video camera section and a recording section are integrally formed as one body on the same chassis completely and mechanically.
2. Description of the Prior Art
In a conventional video tape recorder having a built-in type camera, a video camera section and a recording section are integrally formed as one body on the same chassis, and its signal processing system processes a signal in the form of an analogue signal. Although the signal processing system can process the signal in the form of a digital signal, a so-called digital video tape recorder in which an input signal is recorded on and/or reproduced from a record medium such as a magnetic tape or the like in the form of the digital signal becomes large in size. Therefore, such digital video tape recorder is not suitable for portable use unlike the video tape recorder having a built-in type camera which is usually carried by the cameraman.
For this reason, a video tape recorder having a built-in type camera is proposed, which is formed by the combination of a camera section in which, for example, a signal processing is performed in a digital fashion and a video tape recorder section in which a signal is processed in an analogue fashion and a signal is recorded and/or reproduced in an analogue fashion.
This previously-proposed video tape recorder having a built-in type camera will be described with reference to FIG. 1.
It will be seen in FIG. 1 that an image pickup section, i.e., a camera section 1 is comprised of an image pickup element and a signal processing section while a recording section, i.e., a video tape recorder section is provided, which is generally represented by reference numeral 2. The camera section 1 and the video tape recorder section 2 are integrally formed as one body by some suitable mechanical coupling means, though not shown, to form a video tape recorder having a built-in type camera. Alternatively, a video tape recorder having a built-in type camera might be such that a camera section and a video tape recorder section are perfectly formed within the same chassis.
An image of an object 3 is focused on an image pickup element such as a charge coupled device (CCD) 5 or the like via a lens 4. The CCD 5 is formed as a single plate type in which, for example, R (red), G (green) and B (blue) optical filters, though not shown, are arranged on its front in a checkered pattern. The CCD 5 is scanned by a drive signal from a CCD driver circuit 6 which is supplied with a reference frequency from a reference signal generator 7. The CCD 5 derives the three primary color signals R, G and B. These R, G and B signals generated from the CCD 5 are all in the form of analogue signals and are respectively supplied through R, G and B amplifiers 8R, 8G and 8B to analogue-to-digital (A/D) converters 9R, 9G and 9B, thereby converted to digital signals.
The R, G and B data thus converted to digital signals are supplied to a digital processor circuit 10, in which they undergo digital processings, such as, gamma correction, white clip processing, matrix processing and the like, thus the R, G and B data are converted to a digital component luminance signal Y.sub.D and digital color difference signals (R-Y).sub.D and (B-Y).sub.D. The digital luminance signal Y.sub.D is directly supplied to an adder 12, while the digital color difference signals (R-Y).sub.D and (B-Y).sub.D are supplied to a digital encoder 11, in which they are encoded to a digital chroma signal CD similar to I and Q signals and are interpolated in bit synchronization with the digital luminance signal Y.sub.D. The resultant signal is supplied to the adder 12. The adder 12 is supplied with a vertical synchronizing (sync.) signal and a burst signal from a digital synchronizing signal generator 14 to which the reference signal is supplied from the generator 7 and generates a digital composite signal (composite video signal) CS.sub.D. A sampling clock generator 13 which is supplied with the reference signal from the generator 7 is adapted to generate a sampling clock fc=4 fsc which is used to obtain a subcarrier (referred to hereinafter as fsc). The digital composite signal CS.sub.D from the adder 12 is supplied to a digital-to-analogue (D/A) converter 15 and is thereby converted to an analogue composite signal in response to a clock 2 fsc supplied thereto from a terminal T.sub.3.
While the digital luminance signal Y.sub.D and the digital chroma signal C.sub.D from the digital encoder 11 are digitally added together by the adder 12 as described above, such a variant is also possible that these data are converted to analogue signals by a digital-to-analogue converter and are then added by an adding circuit in an analogue fashion, though not shown.
The analogue composite signal from the digital-to-analogue converter 15 is fed through a video output circuit 16 to an output terminal T.sub.1 as, for example, an NTSC analogue composite signal. It is needless to say that the analogue composite signal may be a PAL or SECAM analogue composite signal.
The camera section 1 is provided with a terminal T.sub.2, and the terminal T.sub.2 is supplied with an analogue composite signal CS from the video output circuit 16.
The video tape recorder section 2 and the camera section 1 are integrally formed as one body as earlier noted and the video tape recorder section 2 will be described next.
As FIG. 1 shows, the analogue composite signal CS from the terminal T.sub.2 of the camera section 1 is supplied to a Y/C separating circuit 17 of the video tape recorder section 2, in which it is separated to provide an analogue luminance signal Y and an analogue chroma signal C. The analogue luminance signal Y is supplied to an FM (frequency modulation)-modulator 18, in which it is FM-modulated and fed through a high-pass filter (HPF) 19 to an adding circuit 20. The analogue chroma signal C from the Y/C separating circuit 17 is supplied to a frequency converting circuit 24. The frequency converting circuit 24 is supplied with a local oscillation output of, for example, 4.268 MHz from an oscillator 25 and converts the analogue chroma signal C of 3.58 MHz into the analogue chroma signal C of low frequency,, i.e., 688 kHz. The thus frequency-converted low frequency analogue chroma signal C is supplied through a low-pass filter (LPF) 26 to the adding circuit 20, in which it is frequency-multiplexed with the analogue luminance signal Y. The resultant signal from the adding circuit 20 is supplied through a recording amplifier 21 to a rotary head 22, thereby recorded on a recording tape 23 as an analogue video signal.
An arrangement of the rotary head 22 is illustrated in FIG. 2A, and as shown in FIG. 2A, the recording tape 23 is obliquely wrapped around a tape guide drum 27 in a tape wrapping angle of about 300 degrees in an ohm-shape via a pair of tape guide members 28a and 28bin order to miniaturize the rotary head 22 or the video tape recorder section 1. This rotary head 22 is rotated at a field frequency to horizontally scan the tape 23 at a frequency higher than a normal horizontal scanning frequency.. thereby recording an output signal of the video camera on tracks 29 of the tape 23 as shown in FIG. 2B.
Incidentally, according to the most popular arrangement of the aforementioned rotary head 22, the tape 23 is wrapped around a tape guide drum in an angular extent slightly larger than 180 degrees and a pair of rotary heads 22, mounted on the tape guide drum with an angular distance of 180 degrees, are rotated at a frame frequency, whereby the two rotary heads 22 are alternately brought in contact with the tape that is transported at a predetermined speed. This type of rotary head is utilized in a portable type video tape recorder which is separately provided from a camera section and it is very difficult to use this type of rotary head in the video tape recorder having a built-in type camera because a tape guide drum and a tape loading mechanism cannot be made light in weight and small in size.
Further, FIG. 3 shows a professional video tape recorder (e.g., Beta Cam, MII, et cetera) which is proposed as an alternative of the arrangement of the video tape recorder section 2. In FIG. 3, like parts corresponding to those of FIG. 1 are marked with the same references and therefore need not be described in detail.
In FIG. 3, it will be seen that the analogue composite signal CS from the terminal T.sub.2 of the camera section 1 is separated to provide the analogue luminance signal Y and the analogue chroma signal by the Y/C separating circuit 17 in the video tape recorder section 2. This analogue luminance signal Y is independently recorded on Y signal recording tracks of the tape 23 by a Y signal recording head 22. To this end, the analogue luminance signal Y is FM-modulated by the FM-modulator 18 and is supplied through the high-pass filter 19 and the recording amplifier 21 to the Y signal recording head 22, thereby being recorded on the Y signal recording tracks of the tape 23 by the Y signal recording head 22. This arrangement can solve the aforementioned problems, such as, low band of luminance signal and cross modulation which are encountered with the low band converted recording system shown in FIG. 1. Red and blue color difference signals R-Y and B-Y involved in the analogue chroma signal are supplied to a 1/2 time base compressor 30. This 1/2 time base compressor 30 is of an analogue type and compresses the red and blue color difference signals R-Y and B-Y by 1/2 under the control of a control circuit 30. Further, according to the 1/2 time base compressor 31, the analogue color difference signals R-Y and B-Y are alternately arranged in that order and the thus time-base-compressed color difference signals are FM-modulated by an FM-modulator 32. In that case, the time-base-compressed color difference signals are supplied through a low-pass filter 33 and a time-base-compressed color difference signal recording amplifier 34 to a time-base-compressed color difference signal recording head 35, thereby being recorded on a time-base-compressed color difference signal recording track adjacent to the luminance signal recording track.
An arrangement of the analogue time base compressor 30 is represented in FIG. 4.
As shown in FIG. 4, the time base compressor 30 is comprised of a delay section 30a formed of four delay elements 30c, 30d, 30e and 30f and a switch section 30b formed of three switches 30g, 30h and 30i. A delay time of each of the delay elements 30c, 30d, 30e and 30f is selected to be 1 H (H is the horizontal scanning period). The first and third delay elements 30c and 30e are supplied with the analogue color difference signal R-Y through a terminal T.sub.9, and the second and fourth delay elements 30d and 30f are supplied with the analogue color difference signal B-Y through a terminal T.sub.10. The switch section 30b is provided at the rear stage of these delay elements 30c to 30f in order that the color difference signals R-Y and B-Y are selected and alternately arranged in the sequential order. In this example, the switch section 30b is formed of the first switch 30g which selects the outputs of the first and second delay elements 30c and 30d, the second switch 30h which selects the outputs of the third and fourth delay elements 30e and 30f and the third switch 30i which further selects these selected outputs. The delay section 30a and the switch section 30b are controlled by the control circuit 31 which is supplied with read and write clocks from a reference clock generator 29.
In the above-described analogue 1/2 time base compressor 30, the delay elements which are placed in the write mode at every line are selected such that the first and second delay elements 30c and 30d are utilized in the case that the odd line is in the write mode and that the third and fourth delay elements 30e and 30f are utilized in the case that the even line is in the write mode. During the period in which the third and fourth delay elements 30e and 30f are set in the write mode, the first and second delay elements 30c and 30d are set in the read mode. At this time, the frequency of the read clock becomes twice the frequency of the write clock by the control circuit 31 so that the input analogue color difference signals R-Y and B-Y are time-base-compressed by 1/2. The first switch 30g is switched in position such that the first half 0.5 H of one line is assigned to the read mode of the first delay element 30c and the second half 0.5 H of one line is assigned to the read mode of the delay element 30d in order to prevent the read modes of the first and second delay elements 30c and 30d from overlapping each other. With respect to the third and fourth delay elements 30e and 30f, the second switch 30h is switched so as to prevent the read modes from overlapping each other similarly as described above. Thus, when the third switch 30i is switched as shown by a broken line in FIG. 4, the reading operation in the odd line is performed and analogue color difference signals with time base compressed by 1/2 are obtained. When the switch 30i is switched as shown by a solid line in FIG. 4, analogue color difference signals with time base compressed by 1/2 are obtained in the even line.
The compressed color difference signals with the time bases thus compressed by 1/2 are alternately arranged in the sequential order and fed through the FM modulator 32 to the color difference signal recording head 35.
According to the video tape recorder having a built-in type camera shown in FIGS. 1 and 2, the diameter of the tape guide drum 27 can be decreased by the amount corresponding to the increase of the tape wrapping angle of the tape 23 around the tape guide drum 27 (e.g., 180/300 if the tape wrapping angle is 300 degrees). According to this system, the video signal of duration in which the rotary head 22 is rotated by 360 degrees must be time-base-compressed by the time-base-compressing ratio corresponding to 300 degrees in which the rotary head 22 is brought in contact with the tape 23. To this end, the scanning speed of the CCD 5 must be increased. More specifically, since the scanning speed of the CCD 5 must be increased under the control of the CCD driver circuit 6 thereby to time-base-compress the video signal of one field to 5/6, this signal does not become the standard NTSC composite signal. There is then the substantial disadvantage that, even when this signal is supplied to a color monitor receiver as it is, the synchronization is disabled.
Further, in the conventional video tape recorders having a built-in-type camera shown in FIGS. 1 and 3, the analogue composite video signal CS of the camera section 1 is supplied to the video tape recorder section 2 as the input signal. This analogue composite video signal CS is frequently utilized by many video tape recorders such as a home video tape recorder and the like so that, when a signal is transmitted from the camera section 1 to the video tape recorder section 2 as the composite signal CS, the video tape recorder section 2 side needs the Y/C separating circuit 17. When such Y/C separating circuit 17 is utilized, if the luminance signal Y and the chroma signal C are not separated positively, a so-called cross color in which the chroma signal C is mixed into the luminance signal Y occurs. Conversely, the luminance signal Y is mixed into the chroma signal C so that a dot interference occurs in the picture at its portion in which the picture is changed rapidly.
Further, in the video tape recorder in which, as shown in FIG. 3, the luminance signal Y is FM-modulated and recorded on one track and the color difference signals are time-base-compressed by 1/2 for the luminance signal, FM-modulated and then recorded on the different recording track so that a video image of high quality can be obtained, the color difference signals R-Y and B-Y are time-base-compressed by 1/2 for the luminance signal Y, which requires the analogue 1/2 time-base-compressor 30 and the control circuit 31 which controls the analogue 1/2 time-base-compressor 30. Also, the arrangement of the 1/2 time-base-compressor 30 and the control circuit 31 needs the reference clock generator 29 or the like and needs a complicated IC circuit.
Furthermore, it is proposed that such time-base-compressor is formed of a digital memory or the like. In that case, such proposal requires an analogue-to-digital converter for converting a composite signal into a digital signal in the video tape recorder section 2, which provides a large and expensive apparatus. There is then the substantial disadvantage that the conventional video tape recorder having a built-in type camera unavoidably needs a large power source in spite of the requirements in which this type of apparatus should be miniaturized and driven by a battery power source.